The invention relates to a switching element for an air intake system of an internal combustion engine.
It is known that at the start of an intake stroke in the air intake system of an internal combustion engine, a vacuum wave is produced which moves upstream in the air intake system. At an end open to the atmosphere or to a buffer provided in the upstream side of the intake system, this vacuum wave is reflected as a positive pressure wave and moves back to the inlet port in the cylinder. By configuring the intake system so that this positive pressure wave reaches the inlet port just before the inlet valve closes, the air is more intensely forced into the combustion chamber, thereby improving the filling of the cylinder. Since the pressure wave moves with a certain velocity, in an invariable intake system it can bring about an optimum filling of the cylinder only within a certain rotational speed range. In order to achieve a good filing in several speed ranges, a plurality of individual air intake ducts are used, which can be opened and closed by a valve. By using different intake duct lengths, different pathways of the pressure wave are produced.
Ernst et al., U.S. Pat. No. 5,696,318 (=DE 19504382) discloses a switching unit for an air intake system with a plurality of inlet passages arranged side by side in an internal combustion engine which has two inlet passages for each cylinder, wherein one passage can be closed with a flap valve and the other passage is always open. The valve flaps of the closable inlet passages are mounted on a shaft which can be moved by a drive unit. All valves of the switching unit are mounted on the same shaft, so that the shaft cuts through each inlet passage, including the unswitched passages. As a result, leakage can occur between the switched and unswitched inlet passages which interferes with the filling effect of the vacuum wave. Another disadvantage of this system is that the shaft constitutes an interfering shape in the unswitched passages, disturbing the air flow and causing turbulence which adversely affects the filling of the cylinders.
The object of the invention is to provide a switching unit for shutting off intake passages in an air intake system, which allows no leakage between the switched and the unswitched flow cross sections.
Another object of the invention is to provide a switching unit which also avoids interfering shapes in the unswitched flow cross sections.
These and other objects have been achieved in accordance with the present invention by providing a switching unit for shutting off inlet passages in an air intake having a plurality of inlet passages arranged side by side in an internal combustion engine, the said inlet passages including at least two switched and unswitched flow cross sections, and wherein each switched flow cross section is provided with a flap valve and all flap valves are opened and closed by a single operating unit which runs outside of, i.e., does not pass through, the unswitched flow cross section.
The switching unit of the invention is advantageously capable of closing a plurality of flow cross sections in an air intake system with a plurality of inlet passages situated side by side in an internal combustion engine and opening them if necessary, while in the closed state no leakage occurs between the laterally adjacent flow cross sections, and the unswitched flow cross sections have no interfering shapes caused by the operating unit. The inlet passages of the intake system can be made in one piece or composed of several housing parts, welded or bolted together, for example.
The switching unit is an area of the intake system which has at least two switched and unswitched flow cross sections, flap valves, and an operating unit. The switched flow cross sections are the areas of the inlet passages in which flap valves are situated and the unswitched flow cross sections are the areas of the inlet passages which lie at the level of the switched flow cross sections but do not have any flap valves. A single operating unit serves to move all of the flaps. The operating unit can be formed, for example, by a single shaft or a plurality of flap valve shafts with a drive unit. The parts of the operating unit are always moved out of the switched flow cross section and operated outside of these flow cross sections. The unswitched cross sections have no contact at any point with the operating unit, so that no connection exists between the switched and unswitched flow cross sections and thus no leakage can occur. To prevent any leakage between the switched flow cross sections, the connection points must be sealed off, which can be done with a gasket, for example.
One advantageous embodiment of the invention comprises a valve flap with a multi-part construction. In this case the valve has at least two flap parts separate from one another, each mounted on a separate valve shaft. The valve shaft can be placed, for example, at an edge portion of the flap part, or be arranged in its center. In the case of a center location of the valve shaft, the shaft and the valve parts are situated in the controlled flow cross section both in the closed and in the open state. If the valve shaft is arranged in the edge areas, the valve parts can advantageously be streamlined so that the valve parts that remain in the switched flow cross section will cause a minimum air turbulence. Possible variants are bulges which narrow the switched flow cross section and widen it again without substantially varying or breaking the lines of flow.
One preferred embodiment of the invention provides for coupling the valve shafts together. The coupling of the valve shafts can be effected by means of a mechanical drive unit which is directly connected to the valve shafts, or by an electronic control of motors which drive the valve shafts. The valve flap shafts can either be counter-rotating, or they can be rotated in the same direction. If the valve shafts are counter-rotating, recesses for the valve parts need only be provided in one part of the intake passage, thereby simplifying the production of the intake passage. If the valve shafts rotate in the same direction, a compensation of the forces involved is achieved, since one valve part turns downwardly and the other upwardly.
In one specific embodiment, the valve parts and their operating units are removed out of the flow cross section when in the open state in order to thereby obtain a smoother flow. The valve parts can be retracted or turned out of the passage. When the valve parts are withdrawn from the switched flow cross section, care must be taken that no leakage occurs. This can be achieved by close tolerances. Another possibility for removing the valve from the flow cross section is to turn the valve parts into recesses provided for this purpose in the passage walls. This will avoid interfering structures and leakage between the switched flow cross sections.
According to another embodiment of the invention, sealing surfaces are provided on the flap valve. The sealing surfaces can seal the flap relative to the flow cross section as well as sealing the flap parts relative to one another. By means of smooth or offset surfaces, the flaps may produce a seal such as, for example, a labyrinth seal. Another possibility for producing sealing surfaces is to provide sealing material on the flap valve. The sealing surfaces are configured such that they seal the flow passage off depending on the particular state. In the closed state the flap valve seals the flow cross section and in the open state it seals the wall of the inlet passage. The use of gaskets at the sealing surfaces is another possibility for producing the sealing of the flap valve in the flow cross section.
One specific preferred embodiment of the invention provides for an offset arrangement of the switched flow cross sections from the unswitched flow cross sections. All switched cross sections lie on an axis so that the valves can be fastened on a single through-shaft so that all valves are operated synchronously. In this case a torsion-stiff material, such as aluminum, is to be chosen for the shaft. The unswitched flow cross sections can likewise lie on one axis, but attention must be given to providing a sufficient distance between the passage wall and the operating unit so as to avoid having any interfering shapes in the unswitched passage or excessively weakening the passage wall to prevent the wall from breaking in operation.
Since the inlet ports in the cylinder head are usually arranged in a row, it is advantageous to provide one switched and one unswitched flow cross section for a cylinder and bring them together ahead of the cylinder in one row lying on one axis. The combining of the two flow cross sections in one row before the cylinder head is a space-saving variant which permits a simple operation of the flaps with one shaft without having interfering shapes to impair air flow in the unswitched flow cross sections.
An advantageous embodiment of the inventive concept involves the operation of the flap valves with one drive unit. The drive unit is then part of the operating unit. In the case of one-piece flap valves, arranged for example on a single shaft, the shaft can be moved by the drive unit, thereby achieving special valve positions or movements. In the case of multi-part flap valves, the individual flap parts are connected together by the drive unit. Thus the flap parts can be operated through the drive unit by a single motor. The valve shafts can be operated in a given transmission ratio. With a transmission ratio not equal to 1:1, variant flows can be produced by having one flap part open faster or wider than the other flap part. Furthermore, drive units are conceivable which move the flaps in translation, whereby the valves are moved out of the flow cross section. For this purpose gear drives or lever drives could be used.
According to another embodiment of the invention, the flap can be placed in a short tube which surrounds the switched flow cross section. This tube is configured so that it can be installed as a preassembled unit into the air intake system and thus the flap can close or open the flow passage as a valve. In particular embodiments of the tube, it can form the entire switch means which can be installed as a preassembled module in the air intake system.
It is especially advantageous to produce the valve flaps and the tube by assembly injection molding, thereby gaining the advantages of assembly injection molding and achieving close tolerances and optimum fit so that virtually no leakage will occur.
One specific embodiment of the invention provides for the use of the switch unit in a substantially rectangular flow passage. The flap valves can then be journaled on integral pivot pins or on a shaft inserted in the edge areas. When the valve is opened the flap parts can be turned into recesses provided for them in the wall of the flow passage.
These and additional features of preferred embodiments of the invention will be found not only in the claims but also in the description and the drawings, the individual features being applicable individually or jointly in the form of subcombinations in embodiments of the invention and in other fields and may represent advantageous, independently patentable embodiments, for which protection is hereby claimed.